<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
        }
        .root {
            position: absolute;
            width: 100%;
            height: 100%;
            background-color: skyblue;
        }
        .bgc {
            display: flex;
            justify-content: center;
        }
        .login-box-body {
            display: flex;
            justify-content: center;
            margin-top: 200px;
        }
    </style>
</head>
<body>
    <div class="root">
        <div class="bgc">
            <h1 class="title">后台管理系统登录模块</h1>
        </div>
        <div class="login-box-body">
            <!-- 注意这里的action是已经到了登录的第二步了 -->
            <form action="/login/in" method="post">
                用户名 <input type="text" placeholder="请输入用户名" id="username" name="username">
                密码 <input type="text" placeholder="请输入密码" id="password" name="password">
                <button type="submit">登录</button>
            </form>
        </div>
    </div>
</body>
</html>